OK - I saw a TV programme on women drinking in pregnancy - it was on some time last year. It highlighted that women were being given different advice, even by people like midwives so there was some confusion.
The academic who had researched the effects of drinking in pregnancy said that although lower amounts of alcohol would not cause full-blown fetal alcohol syndrome, there was some possibility that they could cause more subtle learning difficulties in children.
IIRC, he said that nobody actually knows how much alcohol is safe to drink in pregnancy. Alcohol stays in the baby's blood stream a lot longer than in the adult mother since the baby's liver is not working to break it down and it has to wait until the alcohol is removed via the placenta. He hypothesised that the higher incidence of things like ADHD that we see in children these days may partly be explained by the fact that many more people these day have a glass of wine in an evening, where once they would have had a cup of tea. In places like France where wine drinking has been part of the culture for a lot longer, pregnant women tend to drink just a small amount of wine mixed with water during a meal so were actually consuming a much much lower concentration of alcohol.
He said because nobody could say for certain how much alcohol (if any) was OK, the only totally safe thing to say was that if women did not drink during pregnancy, their baby would not be affected.
The other thing they looked at was although a lot of women thought it was safer to drink alcohol after the first trimester, this just wasn't the case and that actually some of the bad effects were caused by drinking in the third trimester because of how that related to the baby's brain development!
I can't find any links to the programme I saw but this article seems to be saying that people with particular gene variants may have babies that are more susceptible to alcohol damage in utero.
Before I saw the programme I thought that avoiding alcohol completely in pregnancy was totally over the top, but the programme really changed my mind. I wouldn't risk it myself now!